1. Field of the Invention
The present invention pertains to a pressure plate assembly for a friction clutch, comprising a housing arrangement designed to be connected to a centrifugal mass arrangement; a pressure plate held in the housing arrangement with freedom to move axially; a stored-energy element; a wear-compensating device acting in the path of force transmission between the stored-energy element and the pressure plate, where the wear-compensating device has at least one adjusting element able to move in an adjusting direction to compensate for the wear; and at least one clearance-producing arrangement, comprising a gripping element on the pressure plate, which element, when wear occurs, comes to rest or can be brought to rest against a blocking element, which is fixed or can be fixed in place relative to the housing arrangement.
2. Description of the Related Art
A pressure plate assembly of this type is known from, for example, U.S. Pat. No. 6,123,180. In this known pressure plate assembly, the blocking element provided to cooperate with the gripping element of the clearance-producing arrangement is screwed to the housing arrangement by threaded bolts and thus connected tightly to it. For this purpose, the housing arrangement has a specially shaped area, the surface of which is positioned facing the centrifugal mass arrangement and against which an appropriate surface of the blocking element comes to rest when the tightly-screwed connection mentioned above is made. Because of this design, it is necessary to fasten the blocking element tightly to the housing arrangement before the pressure plate and the components cooperating with it or assigned to it are integrated into the pressure plate assembly. This results in the problem that, after the assembly comprising the housing arrangement and the blocking element has been put together with the assembly comprising the pressure plate, the wear-compensating device, and the clearance-producing device, there is the potential danger that the blocking element can interact with the gripping element of the clearance-giving arrangement, this danger being caused by the pretensioning force existing between the housing arrangement and the pressure plate and by the absence of any support for the pressure plate at this stage of assembly, i.e., before the pressure plate assembly has been connected to the centrifugal mass arrangement. The result of such interaction would be the unwanted completion of a wear-compensating adjustment, even though no wear had yet occurred. The pressure plate assembly would then ultimately reach a state in which it could no longer be integrated into a friction clutch by assembly with a flywheel arrangement. It is therefore a familiar and necessary technique in the case of pressure plate assemblies of this type to provide some type of transport-securing devices to ensure that the pressure plate is held in a state in which it is shifted toward the housing arrangement, while at the same time the stored-energy element is brought into a pretensioned state to prevent the undesirable interaction mentioned above between the gripping element and the blocking element. The provision of such transport-securing devices, however, which must hold the stored-energy element in a highly pretensioned position, is a complicated process, especially because of the fact that the transport-securing devices must be massive enough and attached with sufficient permanence that the stored-energy element, which usually generates a comparatively large amount of force, is held securely in the tensioned state indicated above.
It is the object of the present invention to provide measures for a pressure plate assembly which use simple means to prevent an unwanted wear-compensating adjustment of the wear-compensating device before the pressure plate assembly is put together with a centrifugal mass arrangement.
According to the present invention, during or after the connection of the housing arrangement to the centrifugal mass arrangement, the blocking element arrives in or can be brought into a state in which it is able to enter into a blocking interaction with the associated gripping element.
As a result of the design of a pressure plate assembly according to the invention, in which, in the state before the assembly is connected to a centrifugal mass arrangement, the blocking element is ultimately unable to interact with the gripping element, there is basically no danger that unwanted movement of the pressure plate during transport will cause an undesirable wear-compensating adjustment of the wear-compensating device. Because it is impossible for the blocking element to interact with the gripping element, there is basically no need to provide additional transport-securing measures to make sure that the pressure plate is held in a pulled-back position relative to the housing arrangement. The pressure plate could ultimately be held in the desired position relative to the housing arrangement simply by the elements which connect the pressure plate to the housing arrangement such as tangential leaf springs, provided that they are strong enough. But if additional transport-securing devices are to be provided anyway to reduce the load on the tangential leaf springs, for example, these springs would then not have to be strong enough to pull the pressure plate all the way back and hold it there. Instead, a small movement toward the housing arrangement is enough to provide the tangential leaf springs with the load relief mentioned above; and, because of the small extent of this movement or stroke, the force exerted by the stored-energy element in the area of the transport-securing devices is also much smaller.
In a design variant of the pressure plate assembly according to the invention which is especially preferred because of the ease with which it can be manufactured and because of the small number of parts, it can be provided that the blocking element is held in position with respect to the housing arrangement by a fastening bolt element, which fastens the housing arrangement tightly to the centrifugal mass arrangement. It can be provided, for example, that, while the housing arrangement is being tightly fastened to the centrifugal mass arrangement by means of the fastening bolt element, the blocking element is fixed in place with respect to the housing arrangement in a state in which it can enter into a blocking interaction.
In the pressure plate assembly according to the invention, it is also preferable for the blocking element to pass through an opening provided in the housing arrangement, which opening allows relative motion between the housing arrangement and the blocking element; for the area of the blocking element situated inside the housing arrangement to enter into a blocking interaction with the associated gripping element; and for the area of the blocking element outside the housing arrangement to be fixed in place relative to the housing arrangement. Because the blocking element projects outward beyond the housing arrangement, it becomes easier to exert an effect on the blocking element, i.e., either to produce the blocking interaction or to bring the blocking element into a position which allows the blocking interaction to take place.
In this case it is then preferable to provide the area of the blocking element outside the housing arrangement with a pass-through opening for the fastening bolt element.
To make sure that the blocking element cannot come loose from the rest of the pressure plate assembly even in the transport state, that is, before the pressure plate assembly has been attached to a centrifugal mass arrangement, it is proposed that the area of the blocking element inside the housing arrangement be provided with a shape which does not allow this area of the blocking element to pass all the way through the opening provided in the housing arrangement.
So that the interaction between the blocking element and the gripping element already explained above can be reliably excluded in the transport state, it is proposed that, in a situation where the blocking element is not fixed in position relative to the housing arrangement, the area of the blocking element inside the housing arrangement is essentially free to move in the axial direction.
The present invention also pertains to a friction clutch in which a pressure plate assembly according to the invention is provided.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.